An expendable underwater vehicle, such as the Expendable Mobile ASW (Anti-Submarine Warfare) Training Target (EMATT) which is available from Sippican, Inc. of Marion, Mass., is used to train naval forces in the detection, localization, tracking, and/or attacking of a submarine in the ocean (i.e., to train naval forces in anti-submarine warfare). After being launched into the ocean, the expendable underwater vehicle "swims" a pre-programmed underwater course as it acoustically simulates a submarine. The naval forces use acoustics to detect, localize, track, and/or attack the simulated submarine. After a specified time, currently about three hours, the internal batteries of the expendable underwater vehicle become exhausted, and the vehicle drops to the bottom of the ocean. If the water is relatively shallow (e.g., less than about 100 feet), the expended vehicle at the ocean bottom can be washed onto the shore by the action of the tide and currents.
The expendable underwater vehicle can be launched into the ocean from either a surface ship or an aircraft. When launched by a surface ship, the expendable underwater vehicle is dropped into the water from a short distance thereabove such that the impact is minimal and no damage results. In an aircraft launch, the expendable underwater vehicle cannot simply be dropped into the water because the impact with the water typically will damage the vehicle. Additional hardware is used in an aircraft launch to help the vehicle survive the impact with the water. The additional hardware, known as the air launch assembly, includes a two-piece nose cup assembly, a windflap, a harness, and a parachute.
To air launch the expendable underwater vehicle, it is fitted with the air launch assembly. The two-piece nose cup goes over the nose of the vehicle and is held in place by straps of the harness which also attach to the parachute. The parachute is packaged underneath the windflap and the entire vehicle is packaged in a sonobuoy launch container. The vehicle can be launched from the aircraft either using a launching tube that accepts the sonobuoy launch container and automatically, upon command, ejects the vehicle from the container, or by manually removing the vehicle from the sonobuoy launch container and dropping (launching) the unit through a launching tube or other opening in the aircraft. After the vehicle is launched from the aircraft, the windflap separates from the vehicle and deploys the parachute. The parachute opens and decelerates the vehicle such that the vehicle enters the water nose-first and along its longitudinal axis. At or just after water impact, the force causes the two-piece nose cup assembly to separate into its two halves, each of which is forced away from the vehicle as the vehicle continues to descend into the water. The two-piece nose cup assembly: (i) serves as a packaging spacer to contain the vehicle properly in the sonobuoy launch container prior to launch; (ii) keeps the parachute attached to the vehicle after air launch and until or just after water impact; (iii) impacts the water first and thereby helps to protect the vehicle from damage which can be caused by the impact of water entry; and (iv) separates into its two halves at or just after water impact.
After separation of the two halves of the two-piece nose cup, which occurs at or relatively soon after water impact, the vehicle continues to dive into the water at a relatively fast speed such that it can reach a depth of about 100 feet or more before it stops diving. One or both of the halves of the nose cup can contact the rear section (shroud) of the vehicle as the vehicle dives past the separated halves. Because the vehicle is traveling at a high speed as it enters the water (e.g., about 60 miles per hour), the contact can cause serious damage to the shroud which can result in poor performance or even an inoperable vehicle.
The two-piece nose cup assembly can be useful when air launching the vehicle for deep water (e.g., from about 150 to 600 feet) operation. For shallow water (e.g., from about 50 to 150 feet) operation, the vehicle typically must be launched by a surface ship and cannot be air launched with the two-piece nose cup assembly due to the depth to which the vehicle typically descends when air launched with the two-piece nose cup assembly.
Training and practice in the detection, localization, tracking, and/or attacking of a submarine in the ocean (i.e., training and practice in anti-submarine warfare) in relatively shallow waters (e.g., about 150 feet deep or less) can be important to naval forces.